New study says texting doubles a driver’s reaction time

October 5, 2011 -

Researchers at the Texas A&M Transportation Institute have determined that a driver’s reaction time is doubled when distracted by reading or sending a text message. The study reveals how the texting impairment is even greater than many experts believed, and demonstrates how texting drivers are less able to react to sudden roadway hazards.

The study – the first published work in the U.S. to examine texting while driving in an actual driving environment – consisted of three major steps. First, participants typed a story of their choice (usually a simple fairy tale) and also read and answered questions related to another story, both on their smart phone in a laboratory setting. Each participant then navigated a test-track course involving both an open section and a section lined by construction barrels. Drivers first drove the course without texting, then repeated both lab tasks separately while driving through the course again. Throughout the test-track exercise, each participant’s reaction time to a periodic flashing light was recorded.

Reaction times with no texting activity were typically between one and two seconds. Reaction times while texting, however, were at least three to four seconds. Worse yet, drivers were more than 11 times more likely to miss the flashing light altogether when they were texting. The researchers say that the study findings extend to other driving distractions that involve reading or writing, such as checking e-mail or Facebook.

The study, sponsored by the Southwest Region University Transportation Center, was managed by Christine Yager, an associate transportation researcher in TTI’s Center for Transportation Safety. 42 drivers between the ages of 16 and 54 participated in the research.

In addition to the reaction-time element, researchers also measured each driver’s ability to maintain proper lane position and a constant speed. Major findings further documented the impairment of texting when compared to the controlled driving conditions. Drivers were less able to:

safely maintain their position in the driving lane when they were texting and their swerving was worse in the open sections of the course than in barreled sections.

maintain a constant speed while texting, tending to slow down in an effort to reduce the demand of the multiple tasks. By slowing down, a driver gains more time to correct for driving errors (such as the tendency to swerve while texting). Speed variance was also greater for texting drivers than for non-texting drivers.

The fact that the study was conducted in an actual driving environment is important, the researchers say. While simulators are useful, the dynamics of an actual vehicle are different, and some driver cues can’t be replicated in a simulator. By using a closed course, researchers can create an environment similar to real-world driving conditions while providing a high degree of safety for the participants.

“Most research on texting and driving has been limited to driving simulators. This study involved participants driving an actual vehicle, “Yager says. “So one of the more important things we know now that we didn’t know before is that response times are even slower than we previously thought.”

The total distance covered by each driver in the study was slightly less than 11 miles. In the interest of safety for both participants and the research staff, researchers minimized the complexity of the driving task, using a straight-line course that contained no hills, traffic or potential conflicts other than the construction zone barrels. Consequently, the driving demands that participants encountered were considerably lower than those they would encounter under real-world conditions.

“It is frightening,” the researchers wrote, “to think of how much more poorly our participants may have performed if the driving conditions were more consistent with routine driving.”

Federal statistics suggest that distracted driving contributes to as much as 20 percent of all fatal crashes, and that cell phones constitute the primary source of driver distraction. Researchers point to two numbers to illustrate the magnitude of the texting while driving problem: an estimated 5 billion text messages are sent each day in the United States, and at least 20 percent of all drivers have admitted to texting while driving.

The Texas A&M Transportation Institute, headquartered in College Station, Texas, is an agency of The Texas A&M University System.